The present invention relates to multi-layered plastic containers and methods of making such containers. More particularly, the present invention relates to a multi-layered plastic container having inside surface properties that results in enhanced product drainage from the container and the reduction of product residual levels.
Typically, viscous liquid or semi-liquid products are packaged in jars, bottles, tubes, or other containers, and frequently these containers provide a pour-spout or other form of egress for pouring, pumping, or squeezing the product out of the container. Polyethylene (PE) resins have been widely used as favorable material for making packages, for example squeeze bottles, which contain viscous fluids due to their good thermoplasticity, good moldability, and good squeezability. They are also economic, which is an important factor for packaging material, as consumers are usually not willing to pay a significant upcharge for packaging which will eventually be discarded. Certain viscous products have a tendency to stick to or hang-up on the inside surface of these containers, so that a certain portion of the product stays in the container as residue which is thrown out with the container. This results in wasted product and decreases the value the consumer receives from purchasing the product. Therefore, there exists a need to provide a product-contacting inner surface on containers and a particular bottle shape that prompts the product to drain more readily from the container to decrease the residual level.
High product residual levels have been a problem with polyethylene containers, especially when the products contained in the containers are viscous, e.g., oil-in-water emulsions, water-in-oil emulsions, polymeric gels, foams, surfactant mixtures, dispersions, colloidal dispersions, suspensions, polymer solutions, polymer melts, products like catsup, mustard, syrup, etc. Typically, such viscous products are attracted to the interior surface of polyethylene containers. This attraction leads to a residual layer of product remaining on the interior container walls. As a result, a large percentage of the product (from 5% to 25%, or more depending on the ambient temperature and product rheology) cannot be evacuated from the container, and ends up as waste, particularly at cooler ambient temperatures when the products become very thick, almost to the point of non-flowing. Therefore, an object of the present invention is to reduce product residual levels to a level less than about 5% by weight of product initially in the container, which is a reduction of at least 35% by weight as compared to a PE container of similar shape, thereby minimizing the amount of wasted product.
The present invention provides a multi-layered plastic container for containing a viscous product of at least 10,000 cps which provides enhanced product drainage from the container. The container comprises an outer polymer layer providing relative flexibility and structural support, connected to an inner polymer layer having an inner surface that contacts the product and provides for enhanced product drainage from the inner surface. The viscous products suitable for use in accordance with the present invention include water-in-oil emulsions, oil-in-water emulsions, polymeric gels, foams, surfactant mixtures, dispersions, colloidal dispersions, suspensions, polymer solutions, polymer melts, and products like catsup, mustard, syrup, etc.
The inner layer may be formed from polyester, ethylene vinyl acetate, polymethylmethacrylate, a thermoplastic cellulosic, a polycarbonate, polyvinylchloride, polyvinylidene chloride, or Surlyn. The polyester may be either polyethylene terephthalate or glycol-modified polyethylene terephthalate. The ethylene vinyl acetate preferably has a vinyl acetate content of at least about 7.5%, more preferably at least about 12%, and most preferably at least about 18%. The grade of Surlyn, which is an ionomer manufactured by DuPont, may be selected from, but not limited to, 1650, 1652, and 9120. The thermoplastic cellulosic may be cellulose acetate, cellulose acetate propionate, or cellulose acetate butyrate. The plastic container may also include an adhesive layer and a regrind layer.
To further enhance product drainage from the container, the inner layer should have a surface roughness of no more than 0.5 xcexcm.
The present invention is still further directed to a method of draining a viscous content from a package comprising the steps of (a) providing a package as described above; and (b) draining the viscous content as described above.
These and other features, aspects, and advantages of the present invention will become evident to those skilled in the art from a reading of the present disclosure.